Protective apparel has special design and functional needs due to the wide variety of activities that the wearer is engaged in and the wide variety of threats due to the environments to which the wearer is exposed. Protective apparel should exhibit good breaking, tear and abrasion resistance for durability in rugged activities and terrain as well as moisture transport and breathability for reduced heat stress and comfort in hot climates and activities requiring high energy intensity. Additionally, the fabric used in protective apparel must be designed to provide the wearer a wide range of motion in order for the wearer to perform a variety of activities and should provide some environmental protection for the wearer against a variety of climatic conditions. Further, the fabric must be capable of being dyed for aesthetic purposes in most protective apparel and for camouflage purposes in military, tactical, and law enforcement applications. Finally, in applications where threat of thermal hazards exists, protective apparel such as base layers which are worn next to the wearer's skin must provide secondary protection and insulation against fire, flame and heat exposure which might be encountered by the wearer. As used herein, base layer garments include T-shirts, underdrawers, boxers, thermal underwear tops and bottoms, balaclavas, socks, glove liners, shirt bodies, garment panels, and inner linings for outerwear or other garment layers. Base layer garments are intended to provide protection secondary to the primary thermal protection of protective outer garments or other protective garment layers, and a critical requirement for such base layer garments is that the fabrics from which such garments are made will not deteriorate rapidly, shrink, melt, drip or adhere when exposed to elevated temperatures, consequently causing severe injury to the wearer's skin. As used herein the terms “melt” and “drip” shall correspond to the definitions provided for each in NFPA 1975 Standard, Sections 3.3.16 and 3.3.6, respectively. Accordingly, “melt” shall mean a materials response to heat evidenced by softening of the fiber polymer that results in flowing or dripping; and “drip” shall mean to run or fall in drops or blobs.
Protective apparel, like those for commercial apparel use, have historically been fashioned from a wide variety of materials including cotton, rayon, lyocell, acetate, acrylic, nylon, polyester, wool, and silk; a wide variety of flame resistant materials; and combinations of such fibrous materials. Base layers and inner linings in general have typically been made from knitted fabrics. Base layers and inner linings fashioned from one or more types of staple fibers and prepared in the form of knitted fabrics generally involve a balancing of properties. One type of fiber or fabric combination might have both desirable features and/or drawbacks which are different from other combinations of fiber and fabric types. With respect to woven fabrics, blends of nylon and cotton are known in military outerwear for high strength and abrasion resistance with longer wearlife thus increasing sustainability in combat and training (See, for example, U.S. Pat. No. 6,805,957 and PCT Published Application WO/2006/088538).
With respect to base layer garment applications, the use of cellulosic staple fibers in a knitted fabric can provide good flexibility, breathability and feel characteristics, along with some desirable thermal properties. Use of synthetic fibers, such as nylon staple fibers in knitted fabrics, can improve the strength, durability, and moisture management of such fabrics. However, the use of synthetic fibers such as polypropylene, polyester and nylon create a potential hazard when exposed to high thermal threats because they can cause severe skin injury when in molten form. In light of the special requirements for fabrics to be used in protective apparel such as base layer garments, it would be desirable to identify appropriate types of fibers and fiber blends which could be fashioned into particular types of fabrics which are especially useful for such base layers.